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Grip Strength and Subjective Fatigue in Patients With Primary Biliary Cirrhosis
To the Editor: It has been reported that 80% of patients with primary biliary cirrhosis (PBC) experience generalized fatigue.1-2 Although fatigue can significantly affect quality of life, few studies have addressed its etiology in PBC. Some reports suggest that there may be a significant organic component to the fatigue described by patients with PBC,2 perhaps as a result of peripheral muscle dysfunction.3 We sought to examine the relationship between peripheral muscle dysfunction and fatigue in a larger sample of patients with PBC.
Methods
Peripheral muscle function was measured with a grip strength protocol in 18 female patients with PBC. Eight patients reported severe fatigue as assessed by the fatigue impact score (mean score, 85 of 160 possible points)2, 4 and 10 reported minimal fatigue (mean score, 7). We also obtained data from 14 healthy female control subjects who were similar in age. Patients unable to complete the grip strength protocol for nonfatigue-related reasons and those with severe PBC were excluded.
Nondominant hand grip strength was assessed with repeat measurements made every 5 seconds for 5 minutes or until grip strength value reached 50% of the starting value. The median percentage decrease in grip strength per repeat measurement was calculated for each subject.
Results
The initial rested grip strength was similar in fatigued and nonfatigued patients with PBC, and control subjects (median, 18.2 kg [range, 11.2-24.4] vs 19.9 kg [12.9-24.2] vs 18.7 kg [8.0-20.3]; Mann-Whitney, P = .27). In control subjects the median decrease in grip strength per 5-second repeat was 0.7% (range, 0.0%-5.8%). A similar rate of decrease was seen in nonfatigued patients (1.1% per repeat [0.5%-3.9%]; P = .46 vs controls). A significantly greater rate of decrease was seen in fatigued patients (4.0% per repeat [2.1%-10.7%]; P<.005 vs nonfatigued patients, P<.005 vs controls). A significant correlation was seen between fatigue severity and rate of decrease in muscle grip strength (r = 0.69, P<.001 in patients; Figure 1). No association was found between muscle fatigability and liver disease severity (data not shown).
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Figure. Relationship Between Muscle Grip Strength Decrease and Fatigue Severity in Patients With Primary Biliary Cirrhosis
A significant correlation between fatigue impact score and rate of decrease in muscle grip strength among PBC patients (r = 0.69, P<.001).
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Comment
Patients with PBC who complained of fatigue showed a markedly accelerated decrease in muscle function on repeat activity compared with both control subjects and nonfatigued patients. Moreover, there was a strong correlation between the rate at which grip strength is lost and the severity of the fatigue experienced by the patient, suggesting that peripheral muscle fatigability may contribute to the symptom complex experienced by some patients. The etiology of this abnormality in repeat muscle function remains unclear and there appears to be no simple relationship with liver disease severity. We could not exclude a volitional component to the decrease in repeat muscle function, although the finding of normal initial grip strength in the fatigued patients would argue against this. Further studies of peripheral muscle and neuromuscular junction function in PBC-related fatigue are warranted. If a significant peripheral motor system contribution to fatigue in PBC is confirmed, this may suggest new modalities of treatment for this troubling symptom.
Jennifer Goldblatt, BMedSci;
Oliver F. W. James, MD;
David E. J. Jones, MD,PhD
Centre for Liver Research
University of Newcastle
Newcastle-upon-Tyne, England
1. Cauch-Dudek K, Abbey S, Stewart DE, Heathcote EJ. Fatigue in primary biliary cirrhosis. Gut. 1998;43:705-710.
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2. Prince MI, James OFW, Holland NP, Jones DEJ. Validation of a fatigue impact score in primary biliary cirrhosis: towards a standard for clinical and trial use. J Hepatol. 2000;32:368-373.
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3. Varga J, Heiman-Patterson T, Munoz S, Love LA. Myopathy with mitochondrial alterations in patients with primary biliary cirrhosis and anti-mitochondrial antibodies. Arthritis Rheum. 1993;36:1468-1475.
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4. Huet PM, Deslauriers J, Tran A, Fancher C, Charbonneau J. Impact of fatigue on the quality of life in patients with primary biliary cirrhosis. Am J Gastroenterol. 2000;95:760-767.
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Letters Section Editors: Stephen J. Lurie, MD, PhD, Senior Editor; Jody W. Zylke, MD, Contributing Editor.
JAMA. 2001;285:2196-2197.
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